1. Technical Field
The invention is generally related to the field of microfluidics and, more specifically, to microfluidics packages.
2. Background Art
Currently the interface between the macroscopic (“real”) world and the microfluidics world is one of the major obstacles in the practical use of lab-on-a-chip components. There are several problems associated with passing microfluidics samples from the “real” world to a microfluidics device, including sample contamination of associated instrumentation, the desire to decrease dead volume in such devices, and a desire to precisely control the volume of sample required. These problems can be understood by considering the example of handling a blood sample. In most respects it is undesirable that the blood, or any related biological product, can diffuse or otherwise contaminate the instrumentation (pumps, valves, tubes and the like). If contamination occurs, the instrumentation must be cleaned before it can be used for a new sample. “Dead volume” refers to the fluid sample being trapped in connecting tubes, channels or valves associated with the system. In some cases, the amount of available blood or fluid to be tested is limited, making it therefore desirable to keep the dead volume as small as possible.
A conventional method for microfluidics packaging may be illustrated by FIG. 1. FIG. 1 illustrates a package 1 comprising a printed circuit board 2, a microfluidics chip 4 having a series of fluid flow channels 3, a gasket material 6 also comprising a series of fluid flow channels 5, and a microfluidics substrate 8. Substrate 8 comprises fluid inlet channels 10 and 12 and a fluid outlet channel 14. Typically fluid inlets 10 and 12 and fluid outlet 14 are connected to pumps, valves, and the like through tubes or other means. It is clear that the whole package 1 will be contaminated as the fluid product flows through. Dead volume cannot be minimized since tubes are used for connections. In addition, volume control depends on precise external pump control, which is inconvenient.
U.S. Pat. No. 6,082,185 describes a compact fluid circuit card having a main body with internal sensing elements and with fluidic circuit components located on both its front and back surfaces. The cards are described as being made inexpensive enough to be disposable by forming its main body and all of its fluidic circuit components so that they are suitable for being integrally formed in one piece by injection molding from plastic, and by using thin strips of adhesively attached material for the main cover bodies, and valve membrane strip. The patent describes the use of heat shrinkable plastic as one suitable valve membrane material. While the patent does describe prevention of cross contamination between liquids in the card by using plastic valve membranes, there is no provision for preventing contamination of clean areas of instrumentation. Moreover, the patent does not describe packaging of microfluidics systems.
Patent Cooperation Treaty International Publication No. WO 02/18827 A1, published Mar. 7, 2002, describes microfluidics valves which include a microconduit for carrying fluid therethrough and at least one microactuating mechanism for selectively deflecting at least a portion of a wall of the microconduit, thus occluding fluid flow through the microconduit. This publication describes a microfluidics valve that is opened or closed by heating and expanding a flexible material to open and close the microfluidics channels. The flexible material may be selected from materials including, but not limited to, “silicon rubber, natural rubber, polyurethane, PVC, polymers and any other similar flexible mechanism known to those of skill in the art.” This document does not disclose or suggest microfluidics packages or microfluidics chips as those terms are used herein.
U.S. Pat. No. 6,443,179 describes another method for electro-microfluidics systems packaging. The patent describes “a new architecture” relying on two scales of packaging to bring fluid to the device scale (picoliters) from the macro-scale (microliters). The larger package consists of a circuit board with embedded fluidic channels and standard fluidic connectors (referred to as a fluidic printed wiring board). The embedded channels connect to the smaller package, referred to as an electromicrofluidics dual-inline-package (EMDIP) that takes fluid to the microfluidics integrated circuit (MIC). The fluid connection is made to the back of the MIC through etched holes that take fluid to surface micromachined channels on the front of the MIC. Provision is also made for electrical connections to bond pads on the front of the MIC. The patent does describe packaged electro-microfluidics devices, for example in FIGS. 22 and 23 where the packaged electro-microfluidics devices are mounted on fluidic printed circuit boards. Adhesive layers are used to bond different components together. Also described are methods of packaging electro-microfluidics devices such as illustrated in FIG. 26. However in all embodiments described in this patent, fluidic passageways through the adhesive layers do not address the contamination issues resolved in the present invention. Nor does the patent address dead volume issues or small quantity sample issues. Essentially the adhesive films function as gasket materials.
U.S. Pat. No. 6,068,751 describes a microfluidics delivery system that allows control of flow of a fluid through elongated capillaries that are enclosed along at least one surface by a layer of a malleable material. An electrically powered actuator included in the system extends toward or retracts a blade from the layer of malleable material to either occlude or open capillaries. Reservoirs included in the pouch together with the capillaries supply fluids whose flow is controlled by movement of the blades. This patent does describe a microfluidics system in which an actuator portion of a valve does not become contaminated during system operation and in fact the actuator portion of the valves are reusable without cleaning. However, the microfluidics delivery systems of this particular patent require electromechanical valves to stop and start flows of fluids, with components that are irregularly shaped, and do not employ barrier films.